kg (kilogram)
is the only SI
unit that has
a prefix - all
the others
don’t i.e.
A (ampere)
J (joule)
m (metre)
N (newton)
s (second)
V (volt)
W (watt)
Ω (ohm)
Pre-fix
Multiplier
nano (n)
10-9
.000000001
micro (μ)
10-6
.000001
milli (m)
10-3
.001
kilo (k)
103
1000
mega (M)
106
1000000
giga (G)
109
1000000000
Physical
quantity
mass
distance
equivalents
1 Kg
1000g
1g
.001kg
1mm
0.001m
1cm
0.01m
1m
1000mm
1000
m
1km
These
are the
“tricky”
ones
If your quantity (number) has a prefix then you multiply the number part by the
value of the prefix to get units.
Example: 120kJ = 120 x 103 = 120,000 J
Example: 350 mm = 350 x 10-3 = 0.35 m
If you have a number and you would like to use a prefix then you divide the number by the
value of the prefix to get the Number with a Prefix
Example: 0.35m = 0.35 ÷ 10-3 = 350mm
Example: 120,000J = 120,000 ÷ 103 = 120kJ
Divide you page down the middle and label
Before and After (collision).
Draw a diagram!
Write down your formulas
Use “u” for
velocity before
and use “v”
for velocity
after collision
Substitute values:
Remember to look for
stationary objects - their
velocity is zero and that part
of the equation goes away!
Now let LHS (before) = RHS (after)
Then solve for unknown value (i.e. what the
question asked you to find)
Note : the unit of momentum is kgm/s or kgms-1
Note : the formula for momentum is given as p=mv in the Data Booklet
Draw diagram or
sketch
On LHS write
Horizontal
Constant Velocity
s  vt
List known and
unknown quantities
Draw line down
centre of page
On RHS write
Vertical
Constant Acceleration
v u
a
t
Time (t) is common to both horizontal and vertical motion
Constant Acceleration due to gravity
Constant Velocity … (Newton’s 1st Law)
Speed or
Velocity
(ms-1)
constant speed
acceleration
deceleration
constant speed
deceleration
Distance travelled = Area under graph
time (s)
NOTE: v > u gives acceleration; v < u gives deceleration or negative acceleration
Before you begin. Remember that VS= V1 + V2
Now write down what you know and don’t know !
R1
V1
Vs
R2
V2
Use this formula if you can’t use
formula 1.
Look for VS in the question.
There are two formulas
associated with Voltage
Dividers
Try to use formula 1
first.
You need 3 of the 4
terms V1, V2, R1 or
R2.
(VS is not required)
Again, remember that VS= V1 + V2
… you don’t need to use formula 2 twice!
The question will indicate whether the temperature
(Thermistor) or light (LDR) is increasing or decreasing.
Use this information to start your answer e.g “As the
light level falls the resistance of the LDR increases …”
Explain the Science of
the LDR (L.U.R.D.) or
Thermistor (T.U.R.D.)
The LDR or
Thermistor
may be
placed here
– you need
to think how
this affects
step 2
This could be
any output
device, e.g.
relay, bell,
buzzer etc.
LDR1
Vs
R2
V2
Explain How the
Transistor works:Switches ON at the
threshold voltage
0.7 V for npn transistor
1.0 – 2.0 volts for
MOSFET
Copy this from the
Physics data booklet
Cross multiply to
simplify then solve for
the unknown term..
Read the question carefully and
select two of the three terms (ratios)
shown in the formula – you should
end up with a simpler relationship
containing two terms (ratios).
Transformers are not
100% efficient due to
• Heat loss
• Magnetising currents
• Sound (vibrations)
Temperature(T)
Gas
Cooling Curve
Liquid
Solid
time(t)
When material is cooling it gives off heat
energy
When its temperature is increasing the
material is absorbing heat energy
LED numerical questions are usually worth three marks.
The question usually gives the operational or working voltage of the LED
… and the operational or operating current of the LED.
Then it asks you to calculate R
R
Vs
This is
where you
get the
extra mark
The current through R
is the same as the
operating current of
the LED
Remember to include unit Ω
If the question asks you to find a “half life” or “how long
a sample takes to decay” or “the initial or final level of
Activity” then it’s a good bet that you need a …………..
Fill in the
initial
Activity
Divide
previous
Activity by 2
Divide
previous
Activity by 2
Until you
reach your
Final Activity
Activity (units)
Time (units)
Initial
time = 0
0
Add one ½ Life to
previous time
Add one ½ Life to
previous time
Until your reach
your Final time
You will get the Units from the question
To find the number of half lives – count the number of entries you have Made
in the time row, but don’t count the first one (the zero value).
To find the Half Life divide the final time by the number of half lives
½ mark
Initially Vc = Logic 0 (0V)
R1
Not gates inverts Logic to Logic 1 (5v)
This is applied to top of R1
Capacitor charge up to Logic 1 (5v)
½ mark
Not gates inverts Logic to Logic 0 (0v)
This is applied to top of R1
Capacitor discharges to Logic 0 (0v)
½ mark
The process repeats
½ mark
Logic 0 = 0V
Logic 1 = 5V
Timing/ Frequency
determined by R1 and C